An organic electronic device means a device that needs charge exchanges between an electrode and an organic material using holes and/or electrons. An organic electronic device can be categorized into two main groups depending on a operation principle. First is an electric device in which excitons form in an organic material layer by the photons brought into the device from an external light source, these excitons are separated into electrons and holes, and these electrons and holes are used as a current source (voltage source) by being transferred to different electrodes. Second is an electronic device in which holes and/or electrons are injected to an organic material semiconductor that forms an interface with an electrode by applying voltage or current to two or more electrodes, and the device is operated by the injected electrons and holes.
Examples of an organic electronic device include an organic light emitting device, an organic solar cell, an organic photo conductor (OPC), an organic transistor, and the like, and these all need a hole injection or transfer material, an electron injection or transfer material, or a light emitting material for the driving of the device. Hereinafter, an organic light emitting device will be described in detail, however, in the organic electronic devices, the hole injection or transfer material, the electron injection or transfer material, or the light emitting material is used under similar principles.
An organic light emission phenomenon generally refers to a phenomenon that converts electric energy to light energy using an organic material. An organic electronic device using an organic light emission phenomenon typically has a structure that includes an anode, a cathode, and an organic material layer therebetween. Herein, the organic material layer is usually formed as a multilayer structure formed with different materials in order to improve an efficiency and a stability of an organic electronic device, and for example, may be formed with a hole injection layer, a hole transfer layer, a light emitting layer, an electron transfer layer, an electron injection layer, and the like. In the structure of such an organic electronic device, holes from an anode and electrons from a cathode flow into the organic material layer when voltage is applied between the two electrodes, excitons form when the injected electrons and holes are combined, and light emits when these excitons fall back to a ground state. Such an organic electronic device has been known to have characteristics such as spontaneous light emission, high brightness, high efficiency, low driving voltage, wide viewing angle, high contrast and quick response.
In an organic electronic device, a material used as an organic material layer can be categorized into a light emitting material and a charge transfer material, for example, a hole injection material, a hole transfer material, an electron transfer material, an electron injection material and the like, depending on the function. In addition, a light emitting material can be categorized into, depending on a light emitting color, a blue, a green and a red light emitting material, and a yellow and an orange light emitting material to obtain better natural color. Meanwhile, when only one material is used as a light emitting material, problems occur such that a maximum light emitting wavelength moves to a long wavelength due to the interaction between molecules, color purity is reduced, or an efficiency of the device is reduced due to a light emission reduction effect. Therefore, a host/dopant-based material may be used as a light emitting material in order to increase color purity and increase light emission efficiency through the energy transfer.
In order for an organic electronic device to fully exhibit excellent characteristics described above, materials that form an organic material layer in the device, for example, a hole injection material, a hole transfer material, a light emitting material, an electron transfer material, an electron injection material, and the like, need to be supported by stable and efficient materials first, however, the development of stable and efficient materials of an organic material layer for an organic electronic device has not been sufficient so far. Therefore, there have been continuous demands for the development of new materials, and the needs for the development of such materials also apply to other organic electronic devices described above.